1. I think can be done.
2. I don't know which kind of wardrobe you talking about, but as far as I know, wardrobe installation won't damage the floor. Screw will be install to the wall only.

For the stairs, they can cut the frame and cover the holes with something. So not much damage to scrap all the flooring. Wardrobe seem only resting on the floor. Floor might not even damage underneath it. If turn bad might be moisture trap underneath wardrobe.